Eductive dispensing systems designed to dispense multiple chemicals from a common outlet are generally known in the art. These systems generally utilize a centralized control box that is connected to a supply of eductive fluid, which is usually water, a supply of at least two chemicals from which the system can select, and an outlet, for example, a hose connected to a spray wand or nozzle, to dispense the desired mixture. These systems require mechanisms to (1) turn the flow of the eductive fluid on and off, which controls the operation of the entire system and (2) select the particular chemical to be dispensed with the eductive fluid. Prior art systems utilize two separate mechanisms to accomplish these tasks. In addition, the prior art systems generally utilize distinct chemical paths, with a separate eductor for each chemical path, for each chemical connected to the system. This design renders the eductor units in accessible for removal and cleaning or replacement.
U.S. Pat. No. 6,655,401 describes a multiple chemical eductive dispensing system that utilizes a separate selection control and eductive fluid inlet valve. The selection control includes separate eductors, also known as venturis, for each chemical path. This reference does refer to the possibility of turning the flow of all fluid off via the selector switch of the system, but does not describe how this may be done.
The prior art systems also lack a means for preventing the potential contamination of the individual chemical storage containers with the water/chemical mixture when flow of the mixture is shut off at the spray nozzle. When the flow of water/chemical mixture is shut of at the spray nozzle, pressure in the portion of the system below the eductor rises. If the pressure in this system reaches a level greater than the chemical inlet pressure at the eductor, then it is possible for the water/chemical mixture to overcome the inlet pressure and flow back into the chemical supply line. This contamination can result in overly diluted, and, therefore, ineffective, chemical being dispensed from the system.
The present invention is directed to overcoming one or more of the problems set forth above.